This invention relates to prostheses in general, and specifically to the use of a compressible member in a prosthesis such as a prosthetic foot, which compressible member is useful to modify or fine-tune the performance characteristics of the prosthesis. In particular, the compressible member may be juxtaposed to various structural members of the prosthesis to "cushion" or otherwise limit or modify the movements thereof.
Although many prosthetic devices have attempted to simulate the ambulation of a normal foot, virtually all of them are not readily adjustable in terms of their performance characteristics. This adjustability is especially desirable among amputees who participate in a variety of physical activities requiring varying levels of energy-storing and -releasing attributes.
Certainly, some prior art devices more nearly achieve the desired ease of adjustability than do others. For example, see my U.S. Pat. No. 4,547,913 for my invention relating to a "Composite Prosthetic Foot and Leg", and U.S. Pat. No. 4,822,363 for my invention relating to a "Modular Composite Prosthetic Foot and Leg". Also my U.S. Pat. Nos. 5,037,444 and 5,181,932 disclose prosthetic foot devices with similar preferred materials and methods of manufacture, and with corresponding benefits therefrom.
Each of my aforementioned inventions is characterized by lightweight, elongated structures incorporating polymer impregnation of superimposed reinforcing laminae maintained in the desired configurations. Such configurations and constructions provide the desirable characteristics of strength and flexibility in the prosthetic member, and achieve a simulation of the performance of natural feet which had previously not been attainable. Such prostheses may be provided in modular assemblies, whereby the particular performance characteristics of a given prosthesis may be adapted and readily adjusted to meet the needs and activity level of the individual patient.
Notwithstanding the valuable contribution and characteristics of my aforementioned patents and pending applications and specifically the modularity thereof, the adjustment of those prostheses is relatively involved in comparison to that of the present invention. Any adjustment of the performance characteristics of those prostheses broadly requires the disassembly of a covering shroud (if present) and of structural members from each other (through bolt, nut, and washer combinations, for example). After a new combination of structural members has been selected, it must similarly be reassembled.
Other prosthetic foot devices are even less readily adjusted, and include U.S. Pat. No. 3,335,428 to Gajdos, which attempts to duplicate the skeletal and skin structure of a natural human foot, U.S. Pat. No. 2,075,583 to Lange, which incorporates a rubber form mounted in operative relationship with a rigid metallic core, and U.S. Pat. No. 4,645,509 to Poggi, which teaches a prosthetic foot incorporating a monolithic keel or beam of relatively massive proportions intended to react to the load of an amputee's body during walking, running, jumping, and the like and to release the resultant stored energy to create foot lift and thrust complementing the amputee's natural stride.
Moreover, the dynamic performance of most prior art devices is relatively stiff and immediate, and cannot approach the gradual "cushioning" achievable with the use of the bladders of the instant invention in connection with structural members.
Additionally, where bladders have been utilized in prosthetic devices, they have been relatively limited in their performance and usefulness by their configuration. For example, U.S. Pat. No. 708,685 discloses a pneumatic sole 36, FIG. 2, which interacts with pistons 36 (the number 36 was mistakenly used for two different parts in the patent) and 37 and with a section 35 of the sole 36 to mimic flexure and cushioning of a natural foot. In U.S. Pat. No. 1,151,144 to Wofe et al., an air bag 3 (FIG. 4) is filled with air to a desired pressure through a valve 4 (FIG. 2). Both of these patents disclose relatively basic uses of pneumatic devices in prostheses, but include significant shortcomings, such as the apparent likelihood that the wearer may experience a feeling of being "high-centered", especially with respect to lateral stability.